As the rapid development of the heavy industry and the increasing population result that the demand for the thermal power generation have increased. And both the emission of automobile exhaust and the amount of out-door air-conditioner soar. All of these cause the climate warming.
In order to alleviate the discomfort caused by climate warming, air-conditioner and AC motor fan become the necessities of life. Recently many kinds of cooling garment products using different working principle to reduce body surface temperature are appeared in market. The general pattern of the most popular cooling garment is zipper jacket with opening and closing fore breast. The basic technology of the cooling garment is that in use all of the other part of the cooling garment is close except cuffs and neckline. When the power is connected, two small-sized DC fan installed at the circular opening at the left and right ends of the waist in the cooling garment blows in the clothes. The principle is that when the body surface is completely wet by sweat, the fan installed on the clothes transfers air lower than the body surface temperature from outside the clothes into it, and form circulating airflow in the space between the body and the clothes. When the airflow glide along the body surface, it rapidly evaporates the sweat attached to the body surface to produce heat of vaporization effect, therefor reducing the temperature of the body surface. At the same time, the heat in the blood that is contained in the capillaries of the body is expelled from body as the sweat evaporates. This phenomenon is transmitted to the human brain through the epidermal nerve, so the human body feels cool. This series of physiological process constitute so-called physiological effect of human body air conditioning.
However, for the human body, water in the human body is, after all, a valuable and indispensable resource. When the amount of sweat secreted to a certain extent, in order to maintain that the function of other organs of the body will not cause dysfunction because of lack of water, or the body will not cause dehydration symptoms because of the large loss of water, the body will slow down the speed of the secretion of sweat, and less sweat is secreted from the sweat glands. What happens is that very limited sweat is secreted and evaporates instantaneously. So the cool effect at initially using cooling garment will be more and more not obvious. In addition, if the outside temperature of the cooling garment is close to the body temperature, or higher than the body temperature, then use the cooling garment, input equal to or higher than the body temperature of air into the cooling garment, the effect will be counterproductive things.
This shows that the cooling garment can not be durable and effective to cool the human body in the hot conditions.